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The use of yeast gives baked goods (such as breads) both flavor and an airy lightness. Unlike chemical leaveners which react upon contact to produce gases, yeast are living organisms that digest sugars and produce alcohol and carbon dioxide. Because they are living, we promote their growth and their production by providing them with warmth, food (sugars), and time. Yeast is used for a variety of purposes outside of baking (such as for brewing beer, for fermenting wine, and for ingesting as a nutritional supplement) but we'll focus on yeast for baking in this article.

Saccharomyces cerevisiae, baker's or brewer's yeast, are fungi which naturally occur, well, all over the place. Because yeasts are everywhere, it's possible to leave a batter (or grape juice) out and cultivate a new colony of yeast to grow in your food, but this is probably not advisable for most people - especially since yeast (specifically the desirable strain) is commonly available in grocery stores. Although many other strains are generally regarded as safe (S. bayanus and S. pastorianus used extensively in commercial beer and wine making), in cooking and baking, the word yeast refers to S. cerevisiae.

Yeast live by consuming sugars and converting them into energy with carbon dioxide and alcohol as a by product. This is great for baking because if we can provide a stretchy framework, supply sugar, and leave the yeast to grow in a warm environment, the yeast will eat the sugars, convert it into flavorful alcohols, and fill the stretchy material with gases forming air bubbles (and, depending on the activity of the yeast and how strong the material is, large air bubbles). In bread making, the stretchy framework and the food are usually one and the same - wheat flour and water that has been kneaded to produce long strands of interwoven, stretchy proteins called gluten. The yeast, incorporated into the flour and water, consumes the glucose, fructose, and maltose broken down from the starches of the wheat flour and releases carbon dioxide which gets trapped in the network of starch and protein. The build up of these gases causes the dough to "rise".

To allow yeast to feast on just wheat flour and water is time consuming, sometimes taking several days to produce enough flavor and volume of small bubbles for delicious, tender bread. Many recipes aid the growth of the yeast by providing a little extra fuel in the form of cane sugar (be careful, an environment too saturated with sugars can shut down yeast activity resulting in a dense loaf) and making sure the temperature is just right to promote yeast activity (around 95°F [35°C]).

The amount of yeast to use, the length of time to allow the yeast to grow, and the balance of other ingredients that may promote or inhibit yeast activity are all unpredictable variables when creating a recipe from scratch. It takes a lot of trial and error to produce a recipe with accurate rise times for a particular amount of yeast (doubling yeast in a recipe won't allow you to halve the rise time) so it's best to start off by sticking with the amounts and times printed in a recipe before experimenting.

Commercial yeast production starts with a small group of healthy yeast organisms that is carefully grown by providing them with nutrients (supplied to them in a slurry called wort). As they multiply via budding (splitting themselves into new yeast cells), the yeast is transferred from test tubes to flasks to tanks. The tanks (called fermentation tanks) start off small and contain a specially formulated wort (usually a mixture of molasses, minerals, and vitamins) enabling the yeast to reproduce quickly and grow (and to be transferred to ever larger fermentation tanks). Fleischmann's has some multi-story tanks that have a capacity of over 60,000 gallons (225,000 L)! When the producer decides it's more cost effective to sell the yeast than to keep multiplying them, they wash and separate the yeast from the wort and other debris and proceed to prepare them for the different types of yeast products.

There are three main types of yeast available to the home cook: fresh, active dry, and instant.

Fresh yeastFresh yeast are live yeast cells mixed with carbohydrates (commonly corn starch) that has been compressed into small square cakes, wrapped, and refrigerated. The yeast is kept cold so it doesn't grow before being incorporated into a recipe and is only viable for about one to two weeks. After that, the yeast runs out of nutrients and dies. Fresh yeast is the most active (that is, gas producing) of the three types of yeast commonly available. According to Fleischmann's Yeast, a 0.6 ounce (17 g) cake of fresh yeast is interchangeable in a recipe to one packet (1/4 ounce or 7 g) of dry yeast. A 2 ounce cake is equivalent to three 1/4-ounce packets of dry yeast.[IMG]

Use fresh yeast by crumbling the cake into dry ingredients or into lukewarm water or liquid ingredients (70-80°F or 20-27°C).[IMG]

Active Dry YeastIntroduced in the 1940's, active dry yeast was a major innovation in how people would use yeast and bake breads. To make active dry yeast, live yeast cultures are dried after being removed from the fermentation tanks. A protective layer of yeast debris is allowed to coat the coarse clumps of yeast forming the tiny granules. Active dry yeast is simply dehydrated, dormant yeast cells clumped into grains that await reactivation. To revive the yeast, the grains must be soaked/dissolved in warm water (about 110°F or 43°C is considered optimal) prior to mixing with the dough or batter. Active dry yeast changed the world of baking because it was a shelf stable product that had consistent performance when used. Families on the move and cooks who didn't have constant access to a refrigerator could still use yeast once active dry yeast was made available. (Fleishmann's introduced their active dry product shortly after America entered World War II with the intent of providing yeast to soldiers.)[IMG]

To use, simply dissolve in warm water (105-115°F or 40-46°C) before incorporating into the rest of the ingredients. Active dry yeast can be kept at room temperature for a year if unopened but you can freeze the yeast and keep it for much longer. The frozen yeast granules can be dissolved into warm water without thawing first. After opening, the yeast generally lasts about 3 months in the refrigerator and 6 months in the freezer.[IMG]

Instant YeastInstant yeast is the name cookbooks give to the third kind of commonly available yeast - but it's almost never sold under that name. Fleishmann's calls their instant yeast product "RapidRise" while Red Star Yeast uses the label "Quick-Rise". With the popularity of bread machines rising, yeast companies are also selling instant yeast as bread machine yeast. In any case, all of these different names mean the same thing - instant yeast. Instant yeast isn't really instant, it's about 50% faster in terms of rise time. To keep things simple, you just use the same amount of yeast as you would active dry, but you don't have to wait as long to get the same rise (which is why recipes typically say something like "allow to rest until volume has doubled, about 1 hour" because we really don't know how long it's going to take because we don't know if you're using the same yeast as we are). Instant yeast is made in a similar manner to active dry, but the drying process has been altered somewhat. According to Red Star, they use a lower heat to produce more porous granules while Harold McGee's On Food and Cooking claims it's a fast drying process. Whatever the process, the end result is that each yeast granule has more surface area and activates faster than active dry. In fact, they activate so quickly, you don't have to soak them in water first - the moisture of the dough or batter will be enough to get the yeast moving again.[IMG]

When looking at the ingredients of instant yeast, it usually contains sorbitan monostearate and ascorbic acid (an antioxidant used in packaged foods as a preservative; a form of ascorbic acid is commonly known as Vitamin C) as well as yeast. My theory is that to make it a little more "instant", sorbitan monostearate is added as a wetting agent to speed up the absorption of water.

To use, just mix the instant yeast into your dry ingredients and proceed. Best results are achieved if the liquid ingredients are heated to about 120°F (49°C). You can also use the instant yeast in exactly the same manner as active dry (dissolving in warm liquid first). Instant yeast has roughly the same shelf life as active dry.[IMG]

This is an interesting article since I have been experimenting wit different kinds of yeast for making naples style pizza. I came across a website - the artisan (http://www.theartisan.net) and it has a lot of info. about bread and yeast. According to the Artisan, the recommended temp of 120 F for rehydrating bread yeast might be too high-
"Although warm rehydration maximizes the performance of instant active dry yeast, companies such as Fleischmann and Red Star suggest that home bakers use water ranging in temperature from 120 to 130, which is excessive. Since, leaching of cell constituents is minimized during rehydration when water is between 70-100 F, using lukewarm to warm water temperature in the dough is advised.

We have communicated with Fleischmann and have been informed that the vast majority of home baking complaints that Fleischmann receives about yeast failures stem from the dough being either too cold, or held at cold proofing temperatures. While 120° F. is certainly excessive for the experienced baker who has control of ingredients, weights, time and temperature, using this temperature does help the inexperienced baker to achieve a faster proof and and to obtain something tangible at the end of the baking process. It is important to note that Fleischmann's recommendations for their experienced retail and commercial customers are dramatically different, and comport with The Artisan's findings."

from what i gather, yeast will begin to die off at 120 degrees and will be completely dead by 140 degrees.
since i am using a very small quantity of water to rehydrate the yeast and it will be difficult to keep the temperature of the water constant, i find it best to rehydrate the yeast in a small container in a water bath that is kept at 104 degrees for 15 to max 30 minutes. this way, the temp variations will be kept to a minimal

i think the word here is optimal. i have also used ady in recipes without rehydrating and they turned out okay. what we are trying to do here is get the best bread we can make from the yeast used. that is why when we rehydrate, we specify time and temp.

George, if you mean best flavor and look of resulting bread, the biggest improvement may be achieved by slowing down the process. I was able to produce my finest loaves by rising dough in a refrigerator. Each of three rises takes about 8-9 hours.

Proofing yeast achieves different results - speeding up the process. If you need to produce bread faster to meet dinner deadline, proofing may give you advantage.

I do not have any firm statistics on speeding bread-making up by proofing yeast, but have years of making bread without proofing with very good results. For the last 4-5 years I often keep dough in the fridge overnight or during the day for slow rising and like results very much.

Recently there has been great interest in "no-knead bread" in which a major factor is overnight rising. These seems to eliminate the need to knead. Google: "no-knead bread'

There's a brief thread in the forums here about the no-knead bread. I've been experimenting with the dough for the last couple months with varying levels of success. The technique is more interesting to me in the fact that it produces a flavorful hearth bread without the use of a preferment/sponge. Kneading is usually only a couple minutes of work, while the multiple steps involved in producing a great tasting loaf requires planning and making sure you're in the kitchen to do the next step. The No-Knead method is very hands off. I'll be doing an article on it in the near future.

George, if you mean best flavor and look of resulting bread, the biggest improvement may be achieved by slowing down the process. I was able to produce my finest loaves by rising dough in a refrigerator. Each of three rises takes about 8-9 hours.

Proofing yeast achieves different results - speeding up the process. If you need to produce bread faster to meet dinner deadline, proofing may give you advantage.

I do not have any firm statistics on speeding bread-making up by proofing yeast, but have years of making bread without proofing with very good results. For the last 4-5 years I often keep dough in the fridge overnight or during the day for slow rising and like results very much.

Thanks, Greg

greg,
i also have experimented with slow fermentation like you did with intervals of less than a day to three days. i agree with you, from my own experience, 1 day fermentation is better than 2 or 3 days. although, i have heard from people who swears by 3 days fermentation in the refrigerator. i also have experimented with beer yeast and wine yeast. personally, i find beer yeast's fermentation cycle to be much much earlier and stronger (time wise). there was an interesting article about using flor sherry wine yeast for bread to add more flavor. unfortunately red star who makes flor sherry wine yeast discontinued packaging it in small 5 grams packs and i was only able to get some with expiration of dec 2006. the flavor was good but not much rise - could be due to the large amount of dead yeast present. there are other ingredients you can add to the recipe - like diastatic malt powder and asorbic acid (vitamin c). ascorbic acid is used to change the ph slightly ( will not impart an acidic taste like sour dough unless you over added)
personally, regardless of what you do, i will still re-hydrate my yeast to obtain optimal results
george

Recently there has been great interest in "no-knead bread" in which a major factor is overnight rising. These seems to eliminate the need to knead. Google: "no-knead bread'

There's a brief thread in the forums here about the no-knead bread. I've been experimenting with the dough for the last couple months with varying levels of success. The technique is more interesting to me in the fact that it produces a flavorful hearth bread without the use of a preferment/sponge. Kneading is usually only a couple minutes of work, while the multiple steps involved in producing a great tasting loaf requires planning and making sure you're in the kitchen to do the next step. The No-Knead method is very hands off. I'll be doing an article on it in the near future.

Hi michael,
interesting idea and like very much to find out you conclusions. read a little bit about no-knead bread. i think the end result will be small hole and not very elastic bread since the gluten has not been developed through kneading. personally i like chewy bread with big holes and i don't think this will work. i wonder if by varying the gluten percentage you can improve the chewiness even without working the dough. you can purchase pure wheat gluten from health stores and add it to the bread dough to change the gluten percentage.
on a separate subject, i have been trying to make you tial with gluten added bread flour(increased to about 20 percent gluten), salt (1.3%), ammonium carbonate/bicarbonate (don't know which one since it is not specified on the packet)(1.6%), baking soda ((1.6%) alum (1.23% and water (92.9 % hydration). the end products turned out not as puffy like the good ones you get in restaurants. i can increase the puffiness by adding quick rise yeast but the texture and tastes changed slightly. i am wondering if you or your readers know of a good recipe to use. i tried googling it and all the recipes i came across did not work well.
george

i think the end result will be small hole and not very elastic bread since the gluten has not been developed through kneading.

That actually isn't true, George, the beauty of the no-knead method is that it produces an artisanal-style bread with a minimum of kneading. The long, slow rise is similar to a gentle knead as it allows the gluten molecules to align with each other, creating the gluten sheets and webs which contribute to elasticity. The wetness of the dough also helps this to happen as the increased moisture helps the gluten molecules to move.

Additionally, the holes in this bread can be huge--just like a ciabatta, a wet dough with minimal kneading time actually produces large holes. I can't remember the scientific explanation off the top of my head, but I can go look it up if you like.

It's a common fallacy to think that more kneading or kneading by hand = better bread, but this isn't necessarily true in all cases.

i think the end result will be small hole and not very elastic bread since the gluten has not been developed through kneading.

That actually isn't true, George, the beauty of the no-knead method is that it produces an artisanal-style bread with a minimum of kneading. The long, slow rise is similar to a gentle knead as it allows the gluten molecules to align with each other, creating the gluten sheets and webs which contribute to elasticity. The wetness of the dough also helps this to happen as the increased moisture helps the gluten molecules to move.

Additionally, the holes in this bread can be huge--just like a ciabatta, a wet dough with minimal kneading time actually produces large holes. I can't remember the scientific explanation off the top of my head, but I can go look it up if you like.

It's a common fallacy to think that more kneading or kneading by hand = better bread, but this isn't necessarily true in all cases.

Hi Christine,
After reading you msg, I decided to give no knead a try. You are exactly right and it is quite an eye opener for me!
i have made ciabatta different ways before - direct, biga and poolish. I always thought it is no pain no gain, but this is no pain, same (or maybe even better) gain.
My original thinking of small hole and not chewy was wrong. It produced big holes and chewy bread with a crispy skin on the outside! I will definitely try this method for my naples style pizza dough.
I had to vary Jim Lahey's recipe somewhat due to what is available to me:
used caputo 00 pizza flour instead of all-purpose/bread flour because I have a 50 pound bag and has to use it up.
used all-clad stainless steel dutch oven instead of cast iron/enamal/pyrex since that is all i have. heat retention might be better with cast iron.
sprayed some water mist into the dutch oven right before closing the lid and into the oven. this seems to increase the hole size somewhat.
next project - try using cake yeast and adding a small amount of diastatic malt powder to see if this will improve flavor.
Thanks for posting so I have to verify for myself
George

Hey George, I'm glad you tried the recipe and loved it so much. Jim Lahey's method is so revolutionary because it takes all of these concepts which have been known to the bread community for so long, and puts them all together in a completely unexpected way to produce incredible results. Definitely try to use cast iron if you get a chance even if you don't have a dutch oven. I've been doing mine in my cast iron skillet and steaming the bread with another skillet heated on the shelf below, and it's turned out great.

As for your pizza dough, you may have to tinker with the percentages somewhat--the no-knead dough is so wet that it'll be impossible to work into a round.

Also, if you're working with a domestic oven (even with a tile or other heat-retention device on the botton), use all purpose rather than bread flour--the lower heat of a domestic oven can't handle the higher protein of the bread flour, and bread-flour bases baked in domestic ovens tend to turn out a bit tough on the sides and 'floopy' in the centre. Again, it's another explanation I can't remember but can go look up if you like.

I personally have a table-top pizza oven with a stone floor which gets uber-hot (think 800 or 900F hot), and the pizza it turns out is simply incredible. I've been using Alton Brown's pizza dough recipe from I'm Just Here For More Food as well as the Baking Illustrated one with extra-high protein bread flours (15-17% protein). Delish.